A medical instrument generally relating to the subject matter of this invention is known from U.S. Pat. No. 4,830,002, issued May 16, 1989. The known instrument is specially constructed with respect to rotatability of the proximal gripping members or disks, so that, if necessary, the distal members, which may be constructed as forceps members, can be rotated into a more suitable working position, due to the rotatability.
In the known instrument, the axial displaceability of the forceps members, in the case of a stationarily held instrument sleeve and front gripping member, is brought about by the rear gripping member. As the rear gripping member, constructed as a disk, is spring preloaded so that in the inoperative position, the distal forceps members are drawn into the instrument sleeve. The spring tension conventionally determines the forceps force which can be applied on the distal side. As a result of a minimum spacing present between the proximal gripping members, it is still possible, in the case of the known instrument, to increase the spring tension, on gripping or cutting off a piece of tissue with the forceps members, by manually moving the distal gripping member rearwards by inserting the fingers between the proximal gripping members.
However, the latter procedure is not optimum from an ergonomic standpoint, because the front gripping member must be grasped by the fingers on its distal side, whilst the surface of the hand rests against the rear part of the rear gripping disk. The insertion of fingers into the gap between the two gripping members is, consequently, relatively unergonomic.
Other medical instruments, similar to that already mentioned are known from German application 83 19 104.6 Ul, German Patent 170,360, U.S. Pat. No. 86,016 and Swiss Patent 31,672. It is a common feature of these other medical instruments that an operating rod, axially displaceable in the instrument sleeve, is under spring preloading. The operating rod is, in these instruments, rigidly connected to the proximal, rear gripping member. Thus, in order to open the forceps members, it is always necessary to move the rear gripping member axially in the distal direction towards the front gripping member connected to the instrument sleeve. The corresponding spring tension causes the grasping or closing movement of the forceps members to be carried out.